Apparatus and method for forming a coding unit

ABSTRACT

An apparatus and a method for forming a data structure that improves error resilience when applied to the coding of hierarchical subband decomposed coefficients, e.g., wavelet transform coefficients. The texture unit is defined as comprising only those AC transform coefficients that are located in one or more slices in a single subband. The texture unit is defined as comprising only those AC transform coefficients that are across “n” subbands, where “n” is smaller number than the total number of “N” levels of decomposition. A texture unit can also be defined as comprising only those bits from the DC transform coefficients that form a single bitplane.

This is a continuation of application Ser. No. 09/377,383, filed Aug.19, 1999, issued as U.S. Pat. No. 6,970,604 on Nov. 29, 2005.

This application claims the benefit of U.S. Provisional Application No.60/103,081 filed on Oct. 5, 1998 and U.S. Provisional Application No.60/123,600 filed on Mar. 10, 1999, which are herein incorporated byreference.

The invention relates to a data structure in the field of digitalmultimedia communications. More particularly, the invention relates to aformation of a data structure that improves error resilience whenapplied to the coding of hierarchical subband decomposed coefficients,e.g., wavelet transform coefficients.

BACKGROUND OF THE DISCLOSURE

In the field of digital multimedia communications, data streams carryingvideo, audio, timing and control data are packaged into various“packets”. Generally, a packet is a group of binary digits that includedata and control elements which are switched and transmitted as acomposite whole. The data, control elements and other information arearranged in various specific formats.

Examples of such formats are disclosed in various internationalStandards. These standards include, but are not limited to, the MovingPicture Experts Group Standards (e.g., MPEG-1 (11172-*), MPEG-2(13818-*) and MPEG4 (14496-*)), H.261 and H.263. For example, MPEGdefines a packet as consisting of a header followed by a number ofcontiguous bytes (payload) from an “elementary data stream”. Anelementary stream is simply a generic term for one of the coded video,coded audio or other coded bitstreams. More specifically, an MPEG-2“transport stream” packet comprises a header, which may be four (4) ormore bytes long with a payload having a maximum length of 184 bytes.Transport stream packets are part of one or more programs that areassembled into a transport stream. The transport stream is thentransmitted over a channel with a particular transfer rate.

However, transmission of packets over a noisy communication channel,e.g., wireless communication, may cause corruption in the packetsreceived by a receiver/decoder. Furthermore, some data streams orbitstreams carry compressed data that are correlated in a manner suchthat partial loss of a packet may cause the receiver/decoder to discardthe entire packet. Namely, compression methods are useful forrepresenting information as accurately as possible with a minimum numberof bits and thus minimizing the amount of data that must be stored ortransmitted. To further increase compression efficiency, somecompression methods employ “significance-based” information, e.g., asignificance map-value model, to indicate to a receiver/decoder thesignificance of the transmitted information or absence of transmittedinformation. The “significance-based” information is often previouslydefined, e.g., using symbols, such that the receiver/decoder is able todecipher additional information from the transmitted information.However, the loss of compressed data such as “significance-based”information often results in substantial errors when a receiver/decoderattempts to decompress or decode the corrupted data.

Additionally, another compression techniques involves the transformationof an input image into transform coefficients using hierarchical subbanddecomposition. For example, a useful compression technique appears inthe Proceedings of the International Conference on Acoustics, Speech andSignal Processing, San Francisco, Cal. March 1992, volume IV, pages657-660, where there is disclosed a signal compression system whichapplies a hierarchical subband decomposition, or wavelet transform,followed by the hierarchical successive approximation entropy-codedquantizer. A wavelet pyramid, also known as critically sampledquadrature-mirror filter (QMF) subband representation, is a specifictype of multiresolution hierarchical subband representation of an image.

More specifically, in a hierarchical subband system, with the exceptionof the highest frequency subbands, every coefficient at a given scalecan be related to a set of coefficients at the next finer scale ofsimilar orientation according to a structure called a wavelet tree. Thecoefficients at the coarsest scale will be called the parent nodes, andall coefficients corresponding to the same spatial or temporal locationat the next finer scale of similar orientation will be called childnodes.

A typical method of coding these transform coefficients is in “treedepth scan order as shown in FIG. 1, where an image is decomposed intothree levels of resolution. Specifically, the wavelet coefficients arecoded in tree blocks fashion, where each tree block is represented bythree separate “texture units” shown with different shadings. Eachtexture unit is representative of a tree structure starting from thelowest or coarsest AC band to the highest or finest AC bandcoefficients. However, as the image size is increased, each texture unitwill encompass a greater number of transform coefficients such that eachtexture unit is coded using more than one packet. This can cause moreinformation loss if error occurs in one of these packets.

Namely, the loss of a portion of a texture unit, will often cause asignificant error or loss of data. Therefore, there is a need in the artfor an apparatus and method for formulating a data structure or codingunit, e.g., a new texture unit, to packetize such transform coefficientsto improve error resilience, regardless of the packet protocol that isemployed.

SUMMARY OF THE INVENTION

The present invention is an apparatus and a method for forming a datastructure that improves error resilience when applied to the coding ofhierarchical subband decomposed coefficients, e.g., wavelet transformcoefficients. In the present invention, the data structure is referredto as a “texture unit”.

In one embodiment, the texture unit is defined as comprising only thoseAC transform coefficients that are located in one or more rows in asingle subband. For example, a single slice of transform coefficients ina HL₁ subband is collected as a texture unit and then packetized.

In a second embodiment, the texture unit is defined as comprising onlythose AC transform coefficients that are located in all the subbands ofa decomposition level. For example, a single slice of transformcoefficients from each of the HL₃, HH₃, LH₃ subbands are collected as atexture unit and then packetized.

In a third embodiment, the texture unit is defined as comprising onlythose AC transform coefficients that are across “n” subbands, where “n”is a smaller number than the total number of “N” levels ofdecomposition. Namely, the “depth” of a texture unit in terms of subbandis limited to a fixed value of “n”. This allows a larger image to bedecomposed to a greater number of levels of resolution while minimizingthe possibility of having a single texture unit being encoded onto morethan one packet. For example, transform coefficients from the HL₂ andHL₁ subbands can be collected as a texture unit and then packetized.

In a fourth embodiment, if the DC component for each of the colorcomponents (luminance (Y), C_(r) (U) and C_(b) (V)) is coded inbitplanes, then the texture unit is defined as comprising a bitplanefrom any color components. Thus, each bitplane of the DC transformcoefficients is encoded as a single texture unit.

In a fifth embodiment, the packet size varies in accordance with asubband or decomposition level of the hierarchical subband decomposedimage. Namely, in the context of hierarchical subband coding, a smallerpacket size is employed for the lower frequency subbands and a largerpacket size is employed for the higher frequency subbands.

The present coding method and data structures provide error resilience.Namely, if an error occurs in a packet or a portion thereof, the overallamount of information that is lost will be minimized. In fact, it islikely that the receiver/decoder may account for the loss by applyingvarious error recovery methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic illustration of the parent-child dependencies ofsubbands in an image decomposed to three levels within a wavelet treehaving a plurality of texture units as used in the prior art;

FIG. 2 depicts a block diagram of a simplified packet stream system ofthe present invention;

FIG. 3 is a schematic illustration of a texture unit comprising ACcoefficients within a single subband and its corresponding packetstructure;

FIG. 4 is a schematic illustration of a texture unit comprising ACcoefficients across n-subbands (n=2) and its corresponding packetstructure;

FIG. 5 is a schematic illustration of a texture unit comprising ACcoefficients across n-subbands (n=3);

FIG. 6 is a schematic illustration of a texture unit comprising of asingle bitplane from the DC band;

FIG. 7 illustrates a block diagram of an encoding system and a decodingsystem of the present invention;

FIG. 8 is a schematic illustration of a texture unit comprising ACcoefficients from all subbands of a decomposition level and itscorresponding packet structure; and

FIG. 9 is a detailed schematic illustration of a texture unit comprisingonly those bits from the DC transform coefficients that form a singlebitplane.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

FIG. 2 depicts a block diagram of a simplified structure of a packetstream system 200 of the present invention. For illustration, a datastream such as a “transport stream” as defined in accordance with theMPEG standards is used in the packet stream system illustrated in FIG.2. Although the present invention is described below using the transportstream as an example, those skilled in the art will realize that thepresent invention can be applied to any packet streams, e.g., an MPEG“program stream” or any other packet streams in accordance with otherformats. Furthermore, although the present invention is described belowusing the term “stream”, it should be understood that the variousoperations described below may be performed on the entire stream orportion thereof.

System 200 includes an image/video encoder 220 for receiving andencoding video data 210 into an elementary video bitstream. The videoencoder 220 is an encoder capable of generating hierarchical subbanddecomposed coefficients, e.g., wavelet coefficients with or withoutsignificance-based information. The image/video encoder 220 may be asingle image encoder, e.g., a Joint Photographic Experts Group (JPEG)encoder, GIF, PICT, and the like, or an encoder for an image sequence(video), e.g., a block-based or wavelet-based image encoder operating inaccordance with an MPEG standard. Throughout this disclosure the termsimage sequence, images, and video are used interchangeably. In itsbroadest sense, the invention operates in cooperation with any form ofimage or image sequence encoder that would benefit from the presentpacket structures to provide error resilience.

One example of such an encoder is the Sarnoff Very Low Bit Rate (VLBR)encoder, which is disclosed and claimed in U.S. Pat. No. 5,764,805(issued on Jun. 9, 1998), and is herein incorporated by reference. Otherexamples of such encoders are disclosed in U.S. patent applicationentitled “Apparatus And Method For Encoding Zerotrees Generated By AWavelet-Based Coding Technique” (filed on Oct. 24, 1996 with Ser. No.08/736,114), which is herein incorporated by reference.

Similarly, the system may include an audio encoder 222 for receiving andencoding audio data 212 into an elementary audio bitstream. However,those skilled in the art will realize that a plurality of image/videoencoders 220 _(n) and audio encoders 222 _(n) can be employed to producea plurality of elementary bitstreams. In fact, the plurality of videoand audio encoders can be collectively represented by a server 225,which may employ various encoders and/or may simply contain a plurality(or a library) of stored elementary streams in various storage media.Generally, the output of such server contains interleaved programstreams.

In turn, these bitstreams are sent to packetizers 230 of the presentinvention, where the elementary bitstreams are converted into packets.Information for using the packets independently of the transport streammay be added when the packets are formed. Thus, non-audio/video data areallowed, but they are not shown in FIG. 2. It should be noted thatalthough in a preferred embodiment, the present encoder and thepacketizer are implemented in a single module, those skilled in the artwill realize that the functions performed by the encoder and thepacketizer can be jointly or separately implemented as required by aparticular application.

The packets are received and multiplexed by the transport streammultiplexer 240 to produce a transport stream 245. Packets constructedfrom elementary streams that form a program (a group of “PacketIdentifiers” (PIDs) with associated video and audio data) generallyshare a common time base. Thus, the transport stream may contain one ormore programs with one or more independent time bases, where the timebases are used for synchronized presentation. The time bases ofdifferent programs within a transport stream may be different.

The transport stream 245 is transmitted over a transmission channel 250,which may further incorporate separate channel specific encoder anddecoder (not shown). Next, the transport stream 245 is demultiplexed anddecoded by a transport stream demultiplexor 260, where the elementarystreams serve as inputs to video decoder 270 and audio decoder 290,whose outputs are decoded video signals 275 and audio signals 295,respectively.

Furthermore, timing information is also extracted by the transportstream demultiplexor 260 and delivered to clock control 280 forsynchronizing the video and audio decoders with each other and with thechannel. Synchronization of the decoders with the channel isaccomplished through the use of the “Program Clock Reference” (PCR) inthe transport stream. The PCR is a time stamp encoding the timing of thebitstream itself and is used to derive the decoder timing.

As discussed above, the packetizer 230 organizes the bitstream from theencoder into packets for transmission. If the transmission channel 250is noisy, the transmitted packets can be corrupted or partially lost.Although the present invention describes a method for manipulating abitstream to form a particular data structure or packet structure withinthe encoder 220, it should be understood that this operation can also beperformed within the packetizer 230. As such, the implementation of thepresent invention is a matter of designer choice.

Error resilience is particularly important for packets carryinghierarchically decomposed information, i.e., hierarchical subbanddecomposed coefficients. Hierarchical subband decomposition provides amulti-resolution representation of an image. For example, the image isfirst decomposed into four subbands, LL, LH, HL, HH, each representingapproximately a quarter of the entire frequency band. To obtain the nextcoarser scale image representation, the LL band is further divided intofour subbands. The process can be repeated to form a hierarchicalsubband pyramid. It should be understood that hierarchical subbanddecomposition can apply any number of subband decompositions.

Hierarchical subband decomposed coefficients can be packetized intounits called “texture packets” for error resilience. A texture packetconsists of one or more coding units, named “texture units”. Namely, ifthe texture unit is packetized into a single packet, then the packet isreferred to as a texture packet of the hierarchical subband decomposedimage. In the present invention, different embodiments for forming atexture unit are disclosed.

FIG. 3 is a schematic illustration of one or more texture units 320 a-ccomprising of a slice of AC coefficients within a single subband. Itshould be noted that a slice can correspond to one or more rows in asubband. The texture units 320 a-c are also shown disposed within apacket structure 300 separated by markers 325.

More specifically, FIG. 3 illustrates a hierarchical subband treestructure having been decomposed into three levels or scales ofresolution (e.g., 1=0, 1, 2; level 0=HL₃, HH₃, LH₃; etc.), i.e., a slicein a subband is defined as a texture unit. Unlike the prior art, FIG. 3illustrates a texture unit 320 a comprising only a single row ofcoefficients in the HL₃ subband. Similarly, FIG. 3 illustrates two othertexture units 320 b and 320 c comprising two rows and four rows ofwavelet coefficients in the HL₂ and HL₁ subbands, respectively. Namely,the texture unit comprises 2¹ row(s) of coefficients. In turn, each ofthese texture units is also shown as being encoded onto a texture packet300 having a header 310, a plurality of texture units 320.

Although in the present embodiment a single texture unit is shownencoded onto a single texture packet, there may be situations where itis desirable to encode more than one texture unit onto a single texturepacket, e.g., small texture units. In such situation, the packet maycomprise a marker 325 to demarcate the separation of two texture units320.

Alternatively, FIG. 8 is a schematic illustration of one or more textureunits 820 a-c comprising of slices of AC coefficients within subbands ofa particular decomposition level. This texture unit is referred to ashaving a layer-by-layer structure. Again, it should be noted that aslice can correspond to one or more rows in a subband. In turn, thetexture units 820 a-c are also shown disposed within a packet structure800 separated by optional markers 825.

More specifically, FIG. 8 illustrates a hierarchical subband treestructure having been decomposed into three levels or scales ofresolution (e.g., 1=0, 1, 2; level 0=HL₃, HH₃, LH₃; etc.), i.e., slicesin all the subbands of a particular decomposition level are defined as atexture unit. Namely, FIG. 8 illustrates a texture unit 820 a comprisingthree rows of coefficients from the HL₃, HH₃ and LH₃ subbands.Similarly, FIG. 8 illustrates two other texture units 820 b and 820 ccomprising three sets of two rows of coefficients from the HL₂,HH_(2 and LH) ₂ subbands and three sets of four rows of coefficientsfrom the HL₁, HH₁ and LH₁ subbands, respectively. Namely, the textureunit comprises 3×2¹ row(s) of coefficients.

Alternatively, FIG. 4 is a schematic illustration of a texture unit 420comprising of AC coefficients across “n”-subbands (e.g., n=2). Thetexture unit 420 is also shown disposed within a packet structure 400.

More specifically, FIG. 4 illustrates a wavelet tree structure havingbeen decomposed into four levels or scales of resolution (e.g., 1=0, 1,2, 3). FIG. 4 shows an example of “depth 2” texture units, where alltexture units contain the same number of coefficients. Unlike the priorart, FIG. 4 illustrates a texture unit 420 a comprising coefficientsacross two subbands, HL₄ and HL₃. Similarly, FIG. 4 illustrates fourother texture units 420 b through 420 e comprising wavelet coefficientsacross another two subbands, HL₂ and HL₁. In turn, each of these textureunits is shown as being encoded onto a texture packet 400 having aheader 410, a texture unit 420.

Again, although in the present embodiment a single texture unit 420 isshown encoded onto a single texture packet, there may be situationswhere it is desirable to encode more than one texture unit onto a singletexture packet, e.g., small texture units. In such situation, the packetmay comprise a marker 425 to demarcate the separation of two textureunits 420.

Namely, the present texture unit formation yields fixed size textureunits. If an image is hierarchically subband decomposed into “N” levels,a texture unit is formed as a subtree structure of depth “n” (n<N) witha single coefficient as the root of the subtree, where n can vary fromimage to image. The formation of texture units can start either from thehighest AC band or from the lowest AC band. It is possible that (N MODn)≠0, thus some texture units will have only (N MOD n) depth. If thesetexture units are too small, they can be combined with the next textureunit in coding order onto the same packet as shown in packet 400. Withthe new texture unit formation, the coding order of coefficients is suchthat all coefficients within a texture unit are coded before coding thenext texture unit.

FIG. 5 shows an example of “depth 3” texture units that are formed fromthe highest AC bands. In this case, there are four (4) hierarchicalsubband decomposition levels, where the lowest AC band has only onecoefficient as a texture unit that is too small, thus it is combinedinto the next texture unit, forming the text unit with coefficients1-22.

FIG. 6 is a schematic illustration of a texture unit 620 comprising ofDC coefficients that are encoded in accordance with bitplanes, e.g.,four bitplanes for each color components (Y, U, V). The texture unit 620is also shown disposed within a packet structure 600.

In this embodiment, each texture unit 620 is defined as comprising onlythose bits from the DC transform coefficients that form a singlebitplane. For example, the DC component LL₃ for each image can berepresented in three color components: luminance (Y), C_(r) (U), andC_(b) (V).

It should be noted that the color components C_(r), and C_(b) aretypically defined as being one-fourth the size of the correspondingluminance color component.

Referring to FIG. 9, a bitplane b_(n) is defined as comprising thosebits from the DC transform coefficients that are of common“significance”. For example, FIG. 9 illustrates 16 DC coefficients forthe Y color component and four corresponding DC coefficients for each ofthe U and V to color components. The non-zero coefficient values areexpressed in binary form as an example. Thus, the most significant bit(MSB) of each DC coefficient of the Y color component form one bitplane,which also is defined as a texture unit in this embodiment. In turn, thenext bitplane b_(n+1) is formed from the next most significant bit (MSB)of each DC coefficient of the Y color component and so on. Therefore,FIG. 9 illustrates 12 possible bitplanes that correspond to 12 textureunits 620 a-l of FIG. 6. It should be noted that the number of bitplanesis dependent on the maximum magnitude of the DC coefficients. Since theDC band carries more important coefficients as compared to highfrequency AC coefficients, the present embodiment of defining a textureunit for the DC coefficients based on each bitplane greatly increaseserror resiliency. Namely, the lost of one corrupted texture unit willonly result in a partial loss of information for each DC coefficient.Thus, by using various error recovery or error concealment methods,error resiliency can be maximized for the important DC coefficients bydefining each texture unit as comprising only those bits from the DCtransform coefficients that form a single bitplane.

Returning to FIG. 6, although in the present embodiment a single textureunit 620 is shown encoded onto a single texture packet, there may besituations where it is desirable to encode more than one texture unitonto a single texture packet, e.g., small texture units. In suchsituation, the packet may comprise a marker 626 to demarcate theseparation of two texture units 620. Thus, the size, shape and levels ofresolution can be selectively defined for a texture unit in accordancewith a particular application using one of the above texture unitformation embodiments.

Furthermore, as noted above, the importance of the coefficients indifferent subbands (or frequency range) is different. In general, inhierarchical subband coding, the coefficients in the lower frequencybands are more important than the ones in higher frequency bands. Thus,instead of using constant target length for all packets, in oneembodiment of the present invention, the target packet size varies inaccordance with subbands and decomposition levels. Specifically, asmaller packet size is employed for the more important coefficients anda larger packet size is employed for the less important coefficients. Inthe context of hierarchical subband coding, a smaller packet size isemployed for the lower frequency subbands and a larger packet size isemployed for the higher frequency subbands. This embodiment providesgreater error protection because the effect from the loss of an“important” texture packet is minimized due to its reduced packet size,i.e., losing less information for each corrupted important packet.

More specifically, the present embodiment employs a small packet size ofN bits for the lowest frequency subband, e.g., LL₃. Next, the packetsize is increased to “a”×N, where “a” is greater than or equal to 1 forthe subbands of the next decomposition level, e.g., HL₃, HH₃, and LH₃and so on.

It should be noted that in the present invention, the coding ofcoefficients means the coding of the coefficient values and/or thesignificant symbols (e.g., if zerotree encoding is employed).Specifically, zerotree encoding is an example of an encoding method thatemploys wavelet transform to generate a plurality of waveletcoefficients with “coefficient significance information” in the form ofa significance map. The significance map is entropy coded using aplurality of symbols: ZEROTREE ROOT (ZTR), VALUED ZEROTREE ROOT (VZTR),ISOLATED ZERO (IZ) and VALUE. A ZEROTREE ROOT symbol denotes acoefficient that is the root of a zerotree. A VALUED ZEROTREE ROOTsymbol is a node where the coefficient has a non-zero value and all fourchildren are ZEROTREE ROOTS. An ISOLATED ZERO symbol identifies acoefficient with zero value, but with some descendant somewhere furtheralong with a nonzero. Furthermore, if a leave has a zero value, it canalso be assigned as an ISOLATED ZERO. A VALUE symbol identifies acoefficient with a non-zero value, but also with some descendantsomewhere further along the tree that has a non-zero value.

FIG. 7 illustrates a block diagram of an encoding system 700 and adecoding system 760 of the present invention. The encoding system 700comprises a general purpose computer 710 and various input/outputdevices 720. The general purpose computer comprises a central processingunit (CPU) 712, a memory 714 and an encoder/packetizer 716 for encodingand packetizing an image, video and/or audio signal.

In the preferred embodiment, the encoder/packetizer 716 is simply thevideo encoder 220, the audio encoder 222 and/or the packetizer 230 asdiscussed above in FIG. 2. It should be understood that the encoders andthe packetizer can be implemented jointly or separately. Theencoder/packetizer 716 can be physical devices which are coupled to theCPU 712 through a communication channel. Alternatively, theencoder/packetizer 716 can be represented by a software application (ora combination of software and hardware, e.g., using application specificintegrated circuits (ASIC)), where the software is loaded from a storagemedium, (e.g., a magnetic or optical drive or diskette) and operated bythe CPU in the memory 714 of the computer. As such, the encoder/packetizer 716 of the present invention can be stored on acomputer readable medium. In turn, the packets 300 through 600, whichare generated by the encoder/packetizer 716, can also be stored on acomputer readable medium, e.g., RAM memory, magnetic or optical drive ordiskette and the like.

The computer 710 can be coupled to a plurality of input and outputdevices 720, such as a keyboard, a mouse, an audio recorder, a camera, acamcorder, a video monitor, any number of imaging devices or storagedevices, including but not limited to, a tape drive, a floppy drive, ahard disk drive or a compact disk drive.

The encoding system is coupled to the decoding system via acommunication channel 750. The present invention is not limited to anyparticular type of communication channel.

The decoding system 760 comprises a general purpose computer 770 andvarious input/output devices 780. The general purpose computer comprisesa central processing unit (CPU) 772, a memory 774 and andecoder/depacketizer 776 for receiving and decoding a sequence ofencoded images.

In the preferred embodiment, the decoder/depacketizer 776 is simply anydecoders that are complementary to the encoder/packetizer 716 asdiscussed above for decoding the bitstreams generated by theencoder/packetizer 716. The decoder 776 can be a physical device whichis coupled to the CPU 772 through a communication channel.Alternatively, the decoder/depacketizer 776 can be represented by asoftware application which is loaded from a storage device, e.g., amagnetic or optical disk, and resides in the memory 774 of the computer.As such, any of complementary decoders of the encoder/packetizer 716 ofthe present invention can be stored on a computer readable medium.

The computer 760 can be coupled to a plurality of input and outputdevices 780, such as a keyboard, a mouse, a video monitor, or any numberof devices for storing or distributing images, including but not limitedto, a tape drive, a floppy drive, a hard disk drive or a compact diskdrive. These input/output devices allow the computer to store anddistribute the sequence of decoded video images.

Although various embodiments which incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings.

1. A computer readable medium having stored thereon a data structurecomprising: a packet header; and a payload comprising a first textureunit consisting of AC coefficients from a first single subband of ahierarchical subband decomposed image, a first marker after said firsttexture unit, and a second texture unit after said first marker, saidsecond texture unit consisting of AC coefficients from a second singlesubband of said hierarchical subband decomposed image, said secondsingle subband being different from said first single subband.
 2. Thecomputer readable medium of claim 1, wherein said data structure furthercomprises a second marker after said second texture unit, and a thirdtexture unit consisting of AC coefficients from a second single subbandof said hierarchical subband decomposed image after said second marker,said third single subband being different from said first and secondsingle subbands.
 3. A computer readable medium having stored thereon adata structure comprising: a packet header; and a payload comprising afirst texture unit, said first texture unit including AC coefficientsfrom all subbands of a first decomposition level of a hierarchicalsubband decomposed image.
 4. The computer readable medium of claim 3,wherein said data structure further comprises a first marker after saidfirst texture unit, and a second texture unit after said first marker,said second texture unit comprising AC coefficients from all subbands ofa second decomposition level of said hierarchical subband decomposedimage, said second decomposition level being different from said firstdecomposition level.
 5. The computer readable medium of claim 4, whereinsaid data structure further comprises a second marker after said secondtexture unit, and a third texture unit after said second marker, saidthird texture unit comprising AC coefficients from all subbands of athird decomposition level of said hierarchical subband decomposed image,said third decomposition level being different from said first andsecond single subbands.
 6. A computer readable medium having storedthereon a data structure comprising: a packet header; and a payloadcomprising a first texture unit, said first texture unit consisting ofAC coefficients across n subbands, where n represents a number greaterthan one and smaller than a number of decomposition levels of ahierarchical subband decomposed image.
 7. The computer readable mediumof claim 6, where n is two.
 8. The computer readable medium of claim 6,where n is three.
 9. The computer readable medium of claim 6, whereinsaid data structure further comprises a first marker after said firsttexture unit, and a second texture unit after said first marker, saidsecond texture unit consisting of AC coefficients across n subbands ofsaid hierarchical subband decomposed image, said subbands of said secondtexture unit being different from said subbands of said first textureunit.
 10. The computer readable medium of claim 9, wherein said datastructure further comprises a second marker after said first textureunit, and a third texture unit after said second marker, said thirdtexture unit consisting of AC coefficients across n subbands of saidhierarchical subband decomposed image, said subbands of said thirdtexture unit being different from said subbands of said first and secondtexture units.
 11. A computer readable medium having stored thereon adata structure comprising: a packet header; and a payload comprising afirst texture unit, said first texture unit including bits from a firstplurality of DC transform coefficients that form a first singlebitplane.
 12. The computer readable medium of claim 11, wherein saiddata structure further comprises a first marker after said first textureunit, and a second texture unit after said first marker, said secondtexture unit comprising bits from a second plurality of DC transformcoefficients that form a second single bitplane of said hierarchicalsubband decomposed image, said second single bitplane being differentfrom said first single bitplane.
 13. The computer readable medium ofclaim 12, wherein said data structure further comprises a second markerafter said second texture unit, and a third texture unit after saidsecond marker, said third texture unit comprising bits from a thirdplurality of DC transform coefficients that form a third single bitplaneof said hierarchical subband decomposed image, said third singlebitplane being different from said first and second single bitplanes.14. A method for packetizing a hierarchical subband decomposed imagehaving a plurality of decomposition levels, said method comprising thesteps of: (a) generating a packet header with a computer having apacketizer thereon; and (b) generating a payload with said computer,said payload comprising a first texture unit consisting of ACcoefficients from a first single subband of the hierarchical subbanddecomposed image, a first marker after said first texture unit, and asecond texture unit consisting of AC coefficients from a second singlesubband of said hierarchical subband decomposed image, said secondsingle subband being different from said first single subband.
 15. Themethod of claim 14, wherein said payload further comprises a secondmarker after said second texture unit, and a third texture unitconsisting of AC coefficients from a second single subband of saidhierarchical subband decomposed image after said second marker, saidthird single subband being different from said first and second singlesubbands.
 16. The method of claim 14, further comprising converting saidpacket header and said payload into a packet with said packetizer, andtransmitting a transport stream comprising said packet over atransmission channel.
 17. A method for packetizing a hierarchicalsubband decomposed image having a plurality of decomposition levels,said method comprising the steps of: (a) generating a packet header witha computer having a packetizer thereon; and (b) generating a payloadwith said computer, said payload comprising a first texture unit, saidfirst texture unit including AC coefficients from all subbands of adecomposition level of the hierarchical subband decomposed image. 18.The method of claim 17, wherein said payload further comprises a firstmarker after said first texture unit, and a second texture unit aftersaid first marker, said second texture unit comprising AC coefficientsfrom all subbands of a second decomposition level of said hierarchicalsubband decomposed image, said second decomposition level beingdifferent from said first decomposition level.
 19. The method of claim17, further comprising converting said packet header and said payloadinto a packet with said packetizer, and transmitting a transport streamcomprising said packet over a transmission channel.
 20. A method forpacketizing a hierarchical subband decomposed image having a pluralityof decomposition levels, said method comprising the steps of: (a)generating a packet header with a computer having a packetizer thereon;and (b) generating a payload with said computer, said payload comprisinga first texture unit, said first texture unit consisting of ACcoefficients n subbands, where n represents a number greater than oneand smaller than a number of the decomposition levels of thehierarchical subband decomposed image.
 21. The method of claim 20, wheren is two.
 22. The method of claim 20, where n is three.
 23. The methodof claim 20, wherein said payload further comprises a first marker aftersaid first texture unit, and a second texture unit after said firstmarker, said second texture unit consisting of AC coefficients across nsubbands of said hierarchical subband decomposed image, said subbands ofsaid second texture unit being different from said subbands of saidfirst texture unit.
 24. The method of claim 20, further comprisingconverting said packet header and said payload into a packet with saidpacketizer, and transmitting a transport stream comprising said packetover a transmission channel.